In existing integrated circuits (ICs), such as radio frequency ICs (RFICs), etc., inductors are important electronic devices, and property parameters of the inductors may directly affect the performance of the ICs. A majority of the inductors in the ICs may be planar inductors, such as planar spiral inductors, etc. Comparing with conventional coil inductors, the planar inductors have advantages, such as low cost, easy integration, low noise and low power consumption, etc. More importantly, the planar inductors may be compatible with existing IC processes. One important parameter to evaluate an inductor is the quality factor Q.
The quality factor Q of an inductor may be defined as a ratio between the energy stored in the inductor and the energy lost in every oscillating period. A higher quality factor Q may mean that the inductor has a better performance.
One major aspect affecting the quality factor Q of an inductor is the substrate loss. Techniques have been developed to increase the quality factor by decreasing the substrate loss. One of these methods is to form a patterned ground shield between inductors and the substrate on which the inductors are formed. By forming the patterned ground shield, the majority of electric field lines generated by the inductors may be terminated at the patterned ground shield and unable to enter into the substrate, thus the substrate loss may be reduced.
However, in practical applications, although the patterned ground shield may reduce the substrate loss, the quality factor Q of inductors may also be reduced after forming the above patterned ground shield in semiconductor devices having the inductors. The disclosed methods and structures are directed to solve one or more problems set forth above and other problems.